Patent Document 1 discloses a radial type rotor in which a plurality of permanent magnets are embedded in a circumferential direction with a rotation axis being as a center. In the rotor, air gaps are provided at both ends of the permanent magnets in the circumferential direction. An angle defined by an end portion of the air gap on a side closer to a pole center with respect to the rotation axis varies for each pole, whereby cogging torque is reduced.
Technologies related to the present invention are disclosed in Patent Documents 2 to 4.
Patent Document 1: Japanese Patent Application Laid-Open No. 11-98731
Patent Document 2: Japanese Patent Application Laid-Open No. 10-201147
Patent Document 3: Japanese Patent Application Laid-Open No. 2000-69695
Patent Document 4: Japanese Patent Application Laid-Open No. 2002-44888